A right-to-work organization is taking the White House to court over the president’s controversial decision to install three new members on the National Labor Relations Board without Senate approval.

The legal challenge came after the three new members approved a legal response in an existing lawsuit. The plaintiffs asked the judge on Friday to rule that their participation is invalid because President Barack Obama did not have the authority to appoint them.

“We asked [the judge] to consider the question of whether they are constitutionally seated,” said Mark Mix, president of the National Right to Work Foundation.

Without legitimate appointments, they can’t participate in the lawsuit, Mix told The Daily Caller. And without their participation the board does have the quorum needed to implement the new regulations that the foundation opposes.

When the president installed the three officials on Jan. 4, he justified his move by saying the Senate was in recess.

The U.S. Constitution allows the president to bypass the usual Senate debate and vote to appoint officials when the Senate is in recess.

The president’s claim that he can determine when the Senate is in recess is a constitutional issue, he added, because it is an effort to expand the president’s ability to appoint people whose nominations elected Senators oppose.

If not struck down by a court, “that is a dramatic endangerment of the checks and balances in our constitution,” Mix told TheDC.

Only one Democratic Senator, however, has endorsed Obama’s claim that the Senate was, in fact, in recess on Jan. 4 when he announced the installation of the three board members, and of Richard Cordray, whom he had earlier nominated to direct the new Consumer Financial Protection Bureau.

The case is in the U.S. District Court for the District of Columbia. The plaintiffs are arguing against a new regulation directing 6 million small businesses to post specific labor-related information at their workplaces.